Problem: What do the following two equations represent? $-x-y = 4$ $5x-5y = 2$
Putting the first equation in $y = mx + b$ form gives: $-x-y = 4$ $-y = x+4$ $y = -1x - 4$ Putting the second equation in $y = mx + b$ form gives: $5x-5y = 2$ $-5y = -5x+2$ $y = 1x - \dfrac{2}{5}$ The slopes are negative inverses of each other, so the lines are perpendicular.